Sequence studies on both cytoplasmic and mitochondrial malate dehydrogenases from pig heart will be continued. A tentative structure for much of the former has been obtained. The data obtained suggest both possess limited homology to each other and to other dehydrogenases such as lactate dehydrogenase. Because of its superior crystallographic properties, chicken heart mitochondrial malate dehydrogenase is being isolated and structured. The electrophoretic subforms of mitochondrial malate dehydrogenase have been characterized as desamidation products by means of the serum enzyme trans-glutaminase. Isolation and characterization studies on D-3-phosphoglycerate dehydrogenase are continuing. The amino acid sequence of E. coli alkaline phosphatase is complete except for a segment of about 60 residues. The sequence of crab collagenase, which also possesses chymotryptic and tryptic specificity, is in progress. Sufficient data has been obtained to establish it as a homologous member of the serine protease family. Structural studies on the biotin carrier protein of E. coli and the purple membrane protein of H. halobium are in progress.